A commercial for Kraft Dinner from 1989, around when the song was written
Kraft Dinner is a packaged macaroni and cheese product sold in Canada by Kraft Foods, famously referred to by Barenaked Ladies in their song "If I Had $1000000".
At the end of the song's second chorus, the song's narrator sings If I had $1000000, we wouldn't have to eat Kraft Dinner / But we would; the idea being that despite being wealthy, they would still eat the notoriously inexpensive product.
The product
In Canada, Kraft Dinner is the most recognizable brand of boxed mac & cheese, to the point of being considered something of a national dish. The brand name "Kraft Dinner" is unique to Canada; in the United States, it's sold as Kraft Macaroni & Cheese Dinner, and in the United Kingdom it's called Cheesey Pasta.
KD, as it's often known, is notoriously inexpensive, usually priced at less than $2 for a box meant to contain 3-4 servings. The product is thus seen as a symbol of poverty, something that a millionaire wouldn't need to eat, but might anyway if they chose to. Each box contains uncooked macaroni pasta and a bag of powdered processed cheese, which is meant to be mixed with butter and milk to make the sauce.
Kraft first began selling packaged macaroni and cheese in 1937, during the Great Depression. This, combined with World War II food rationing, made the product extremely popular as a filling, easily prepared and inexpensive meal that could keep for long periods of time with no refrigeration. The iconic blue packaging was introduced in 1954.
Projectile pasta
BNL performing "$1000000" at a concert in Britain, in which Steve is presented with a box of "Cheesey Pasta"
Beginning in the early 1990s (by some accounts, at a particular show at Toronto's Danforth Music Hall in 1991), fans of BNL began throwing boxes of Kraft Dinner onstage during performances of "If I Had $1000000" after the line about KD was sung. Though amusing at first, the practice eventually got out of hand, with the band often having to dodge multiple sharp-cornered boxes and potentially explosive packets of cheese powder. One story from the Stunt tour even has touring keyboardist Chris Brown find cooked cheese sauce inbetween the keys of his vintage Hohner Clavinet keyboard.
In an effort to discourage the practice, the band would often post signs at the entrances of concerts reading:
Macaroni & Cheese Hurts
When you get it in the head
BNL would appreciate donations to the food bank instead
Thank You
...along with a donation bin for the local food bank. Venue security staff were also instructed to search audience members for boxes of KD. "Those in the know don't throw" became a popular slogan among fans.
Trivia
- The cheese mix in "Original" flavour Kraft Dinner used to contain artificial yellow food dye, giving the finished product an unusually bright orange colour that some found unnatural and disturbing. Kraft began phasing out the artificial colouring (along with artificial preservatives) in 2015 in favour of natural food colouring made of paprika, annatto and turmeric.